The present application relates to a nonaqueous electrolyte secondary battery, and more particularly to a nonaqueous electrolyte secondary battery with a safety valve (safety mechanism), more specifically a safety cover.
As one example, a nonaqueous electrolyte secondary battery is known in which a safety valve 50 is constructed as shown in FIG. 8. A disk holder 53 similar in shape to a safety cover 51 is put over the safety cover 52 such that a protrusion 52 of the safety cover 51 is contained therein, and a stripper disk 54 similar in shape to the disk holder 53 is put over the disk holder 53 such that the disk holder 53 is contained therein (see, e.g., Japanese Unexamined Patent Application Publication No. 2001-307706 (hereinafter referred to as “Patent Document 1”)).
As other examples of nonaqueous electrolyte secondary batteries, batteries constructed similarly to the example shown in FIG. 8 are known (see, for example, Japanese Patent Publication Nos. 2701375 and 3555240 (hereinafter referred to as “Patent Documents 2” and “Patent Document 3”, respectively), and Japanese Unexamined Patent Application Publication No. 2001-325942 (hereinafter referred to as “Patent Document 4”)).
However, in each of the known nonaqueous electrolyte secondary batteries disclosed in the Patent Documents 1, 2, 3, and 4, the safety cover, the disk holder, and the stripper disk are stacked. Thus a height between an upper surface of the safety cover and a lower surface of the stripper disk is so large that this stacked body juts into an internal space of the battery, thereby reducing the internal volume and thus making it likely to preclude a higher battery capacity.